1. Field of the Invention
The present invention relates, generally, to a universal holding fixture, and more specifically, to a universal holding fixture that employs the linear actuator of the present invention.
2. Description of the Related Art
During any given manufacturing process, there may be a need to fix a workpiece in a specific position, especially during precision cutting, trimming, drilling or welding operations, or the like. For example, in the automotive and aerospace industry, it is often necessary to perform various manufacturing processes on large workpieces or on a pair of workpieces that are to be joined or otherwise coupled together. During this process, each workpiece must be precisely located and then held in a predetermined position. It is therefore known to use dedicated fixtures having clamps and locating pins or other devices for this purpose. Such dedicated fixtures are known as “hard tooling.” Where large workpieces are involved in cutting, trimming, drilling, welding or other manufacturing operations, the workpiece must be clamped or otherwise fixed at a number of positions across its surface area. Often, these clamps or mounting points must be engineered so that they do not interfere with the manufacturing process. Accordingly, the clamps and mounting points must be located such that they are not in the path of the cutting, trimming, drilling or welding operations, to name just a few. Thus, hard tooling of this type is often specific to the particular workpiece in question and cannot be utilized to fix, locate and hold workpieces other than the ones for which they were specifically designed. Unfortunately, such hard tooling is relatively expensive and has a useful life that is often limited by the life of the particular workpiece or the end product that employs the workpiece. In manufacturing environments where the design of the end product is constantly evolving or changing, the cost of hard tooling is a particularly noticeable burden on the overall cost to produce many products.
In view of the limitations associated with hard tooling, more flexible fixtures have been proposed and developed in the related art. These devices are sometimes referred to as “programmable tooling” or “programmable fixtures.” There are many varieties of programmable tooling and they are typically distinguished by the particular problem solved or industry served. However, the programmable fixtures of the type generally known in the related art are all characterized by the ability to be used on or in connection with more than one workpiece. Thus, the lifespan of this type of tooling extends beyond a particular design of the workpiece involved.
For example, one type of programmable tooling known in the related art includes a two-dimensional array of linear actuators that may be actuated to engage and hold a workpiece or a pair of workpieces upon which any given manufacturing process is to be performed. The linear actuators may be programmed to adapt to the irregular surfaces of any given workpiece and may be reprogrammed for use with a different workpiece having a different profile.
While programmable fixtures of this type have generally worked for their intended purposes, some disadvantages remain. For example, while the tooling may be programmable so that it can adapt to workpieces of different size and shape, the programmable fixtures of the type commonly known in the related art are typically not capable of reacting to a manufacturing process to actively move a holding or locating component, such as a linear actuator, out of the path of a cutting, drilling or welding operation and then to move the locating component back into a predetermined holding or locating position relative to the workpiece after the operation has passed. Rather, the linear actuator located in the path of any given manufacturing processes are typically programmed not to engage the workpiece in the first place. In this way, any conflict with the manufacturing process is avoided. Moreover, the linear actuator of the type typically employed in programmable fixtures known in the related art generally do not have the capability to identify the exact location of the workpiece nor the exact location of any subcomponent of the workpiece. In addition, while the linear actuators known in the related art have generally worked for their intended purposes, they suffer from the disadvantage that they can deflect from their designed location when they are in the extended position and subject to heavier loads. The linear actuators and programmable holding fixtures known in the related art also tend to be rather complex devices that are expensive to build and maintain.
Accordingly, there remains a need in the art for a holding fixture that is flexible and may be employed in connection with different workpieces in subsequent or different manufacturing processes. Thus, there remains a need in the art for a holding fixture that is universal and may be employed in a number of different environments on a number of different workpieces. Moreover, there remains a need in the art for such a holding fixture that employs linear actuators to quickly fix the workpiece and to establish a datum at a plurality of points relative to the workpiece to precisely locate it. In addition, there remains a need in the art for a universal holding fixture that employs a linear actuator that not only fixes and locates the workpiece, but which may be quickly and efficiently moved relative to the workpiece during different manufacturing operations such that these operations may proceed unimpeded by the presence of the linear actuator. There also remains a need in the art for a universal holding fixture that employs an electronically controlled linear actuator having a pneumatic control module for delivering both positive and negative pressure at the workpiece. Finally, there remains a need in the art for a programmable holding fixture and associated linear actuator that are robust, yet are relatively mechanically simple having a reduced number of components and, accordingly, reduced cost of manufacture.